Compressor blade and method of forming same



Nov. 11, 1958 E. P. WARNKEN 2,859,936

COMPRESSOR BLADE AND METHOD OF FORMING SAME Filed March 3, 1954 3Sheets-Sheet 1 IN V EN TOR.

ELMER WARNKEN BY 0 m 9 V Y Y Azys.

Nov. 11, 1958 E. P. WARNKEN I 5 ND METH D OF FORMING SA r 5% IN VEN T 0Rv ELMERPWARNKEN NW, H 1958 E. P. WARNKEN 2,859,936

COMPRESSOR BLADE AND METHOD OF FORMING SAME :5 Sheets-sheaf 3 Filed Marhs. 1954 INVENTOR. ELMER R WARNMEN United States Patent zesi'sss comnasson time Animyniinoij 6F FoRMiNG SAME eingi P.' wanna, Cincinnati,oifiaass'aasats era-an nati Testing & Research Laboratories,ilincinnati, Ohio; ii l iartiisliip Application March 3 19 54,-SerialN6. 413,743

Claiins. c1. ass- '77 Th s i t ar aw cm lade tmra a pre ses; bl we Q lde le; M te r'at iqu y. th tent oare a bm'n e 'q l e ies 'a i its.pressprs and to a method for making such compressor da g t. ten 'fbie aflfi n e i n, s t P a e1 a l l blade composedofa resin whichisreinforced by e'lon gated glass fibres that extend the length of the addand areprestressed ir tension so that the body at the blade isstre'ssedin corih'pres'siorn thereby giving the body of the b l thestrength required t6 carry the load tau-sea by cen fng' al force' I Afnrth e r object of this invention i s to provide a blade of this typein which the fibers extend lengthwise of the blade are of folded doubletform, the fold of the doublet being at the root at the blade. I A:fnrther object of this invention is to" ieviaei are; stressedcornpressor blade having a core of reseessea lengths of fibre glassmaterial anda skin ar'oiiridth' tria ter ial which gran is formed ofamiiiture of res n and short staple glass fibres the pres tress'edlengths of fibre glass material stress'ihg th resin and the shaft staplefibies in compression. v r v A further object of this invention is; tepr'oyidea blade of this type in which a rigid-pin extends the folder thedoublet so that the folded end i thereby rendered thicker than theremainderof the blade, an shaped to form a retaining key at the robt endof the blade;

A farther object of this inventior'i is' o provide a blade of this typein which the pin is a pager slotted key member h ving a key pbitiohand apin portion spaced fr'en'i each other by thef ;s1dt and iii which thelengths of fibre glass materiai extend thrdtigh the slot of the keymember. u h r Ahd a further ghje'c't of this invention is to provide" amethod of forming a prestres'sed blade having a core of lengths ofresindinpregnated fibre lass material arid a skin formed of resin andshort staple fibres which includes the steps of disposing the lengths ofmaterial in an elongated mold, and, while in the mold, stressing thematerial in tension and injecting into the mold a miiiture of resin andshort staple" gla'ss' fibres to impregnate and cover the lengths ofmaterial; aiid then curing the resin to form a hard, infn'siblepr'es'tres sed resin bladeandbla'de rbo t.

The above and other objects and features or the invention will beapparent to those havin'g' or'dinary' skill in the art to which itpertains from the renewing detailed pt e n hedtw a n whi is l s a a atiiev s .ShQ et mr' s q blade constrncte'd iri accordance with anembodiment of s n s. a 7,, .7. it it Big. 2 is a plan view of a mold forforming the blade; 4 Fig. 3 is a view in section taken on the line Hi-III in Fig. 2, pres'tresis'ed rovings being shown in the mold inposition after mo lding; I Fig. 4 is a view in section taken on the lineIV-'IV in Fig. 3;

2,859,936 Fatented Nov. 11, 1 958 Fig. 5 is a perspective view'showirigari alternate forni er pin for nse'in forming the blade;- y r rFig. 6 is a" schematic view showi'g the operationof the prestressingmechanism of the mold;-

Fig. 7 is a schematic v' lew showing; a porti'o' i of the rotor afar;axial flow air compressor with one or the blades -mountedthereon; m l

Fig. 8 is a perspective View showing a blade-' coil struc ted inaccordance with aii'other etnbo'dirfft':fit of the invention;

Fig. 9 is a perspective view showingthepin ofthe Blade iiltistratedinFi'g. 8; 1

Fig. 10 is a fragmentaryperspective view showing" the arrangement ofrovings on the pinp're'pa'ratbry to the moldingof theblade illustratedinhi'gt'sz Y Fig; 11 isa View in vertical sectiomshowiiig the'rnb'l'd'used'iri forming the blade illustratedirrFig. 8;

Fig: 12 is a fragmentary sectional view of the blade illhstrated'in'Fig.8'; i i i Fig." 13 is a perspective view showinga blade' con-T structedin accordance with another embodimentof this" invention;

Fig; 14 is a perspective View showing a key andpin' member Which formsapart of the blade illustratedfin' Fig;;;1'3; I f

Fig; 15 isja perspective'view 'showing'the arrangement of elongatedro'vings ofl the key and pinmeinber'prior to the molding of the bladeillustrated in Fig. 13;

Fig; 16 is' a fragmentary sectional view showing the mold for moldingthe blade illustrated ,in Fig: 13, the mold being shown before theinjection of resin andshort staple glass fibres; i t, t

Fig.- 17 is a sectional view showingthe mold of Fig. 16 followinginjection; H

, Fig. 18 is an exaggerated sectiojnal view of the blade illustrated inFig. 13; and

Fig. 19 is' a schematic view showing the arrangement of rovings and pinused in molding the blade shown in Figzlt in the following detaileddescription,- and the drawings,- like reference characters indicatelikeparts I r In F s 1 t o n. a, ca re v th de? r' axial-flow aircompressor, such as the gornpressor section of a jet'aircraft engine.The blade 2 comprises avane portion 16 of airfoil configuration-and aroot end portion o generally t dr s a -i ,Th s e s. t fl isd to bemounted 'n a slot 13 'n arotor ring 14 of a-compressor; as showrrin Fig.7,.

In the formation or the blade 9, lengthslofelongated fibre glassmaterial 16 (Fig. 19) of resin-impregnated glass fibres are arranged indoublets. throi' 'gh the lo'o'poi fold of which a pin 17 extends. Thematerial may be fibre glass fabric or Woven clothl, Preferably, the material is in the form of elongated rovings which extend lengthwise of theblade. The fibres of the material may be coated with athermo-settingresimby dipping the same in the resin. As indicated inFigs. 3 and 6, the mat ial 16 and thhe pin 17 are, placed in a lowermold rnembe'r 18. The free or blade" tip ends of the material areclamped to mold member :18 by means or" a clamp plate' 19 securedtomernber. 18 by means rma hines rew 2. wh n i ,1 slqc ed Slots z i n 2n' he mold member 18, he material is stressed in tension, as will beexplained. p i r! As indicated in Fig. 6, the distance f rom t M1 the upe d of the t 1 3 .23 3 haw the distance B to the lower ends of theslots; Thus when the pin 17 is advanced downwardly into the slots 22 and23 the rovings are stressed in tension. When the material is stressed, aspace 24 opens between the converging portions 24a and 24b of therovings. A plug 24' of resinimpregnated glass fibres may be disposed inspace 24 to provide material for filling this space when the blade ismolded (see Fig. 19).

The mold member 18 is provided with a molding surface or face 25 whichis of airfoil configuration for molding the vane portion of the blade.At the left hand end of the face 25 is provided a rounded mold portion25' for molding one face of the root end of the blade. When the pin andfibre glass material are positioned in the mold, a movable mold member26 is actuated by a ram 26' into the cavity of the lower mold member 18against the material and the fold containing the pin 17, whereby the pinis forced into the bottom of slots 22 and 23 and the material isstressed in tension, and the resin is molded and set. When the plungeris raised, as indicated in Fig. 3, the resin holds the material inprestressed condition.

The lower face of the plunger 26 is provided with a mold cavity whichmates with the molding face of the lower mold member to form the blade.While pressure is applied to the mold by ram 26', the prestressedmaterial and resin are heated to sufficient temperature and for asufficient time to cause curing of the resin, and theresin, when cured,holds the material in prestressed condition and forms a hard, smooth,infusible blade surface. After curing, the blade is removed from themold and trimmed to the final shape of a finished blade as shown in Fig.1.

In the finished blade, the tension of the fibre glass material stressesthe resin of the blade in compression. Preferably the blade isprestressed to sufficient degree so that the prestress load on the bladeis greater than the design load level to be produced in the blade inactual use. Thus, when the blade is mounted in the rotor ring 14 and inactual operation, the prestress load maintains a compression in theresin of the blade. 7

As shown in Fig. 1, ends 27 of the pin 17 project beyond the ends of theblade. The ends 27 may be retained, as shown in Fig. 1, or, if desired,the ends 27 may be trimmed off flush with the ends 28 of the blade (onlyone of which is shown).

The pin of the blade described to this point is shown as a round pin. Ifpreferred, a pin of the form shown in Fig. 5 at 30 may be used insteadof a round pin. The pin shown in Fig. 5 includes a main portion 32 oftear drop shape. At the ends of the main portion 32, integral roundedportions 33 and 34 are provided. The portions 33 and 34 are receivablein the slots 22 and 23 of the mold 18. When the pin of Fig. 5 is used,the blade is formed in the same manner as when pin 17 is employed, butin that case pad 24' is not required as the pointed portion 36 of thepin 30 fills the gap between the layers of material atthe root end ofthe blade.

The blade illustrated in Fig. 1 is of particular use where a slot 13 ofthe special shape shown in Fig. 7 may be employed for receiving the rootend of a blade. However, for some purposes, a blade 38 of the shapeillustrated in Fig. 8 is more desirable because the blade illustrated inFig. 8 can be used with rotors constructed to employ conventionalblades. The blade 38 shown in Fig. 8 includes a metal pin member 39 (seeFig. 9). The pin member 39 includes a main portion 41 of tear dropshape, and root-strengthening rib members 42, 43, and 44. In theformation of the blade illustrated in Fig. 8, the pin 39 extends throughthe loop of the doublets of glass fibre rovings 46 or the like, in themanner shown in Fig. 10, and the rovings and pin are positioned in amold, as shown in Fig. 11.

The mold of Fig. 11 includes a lower member 47 and an upper member 48.The mold contains a mold cavity 49 between members 47 and 48. Theelongated rovings extend through an opening 51 ,at one end of the mold 4cavity and are clamped by an appropriate clamp 52. The clamp 52 is urgedto the right, as shown in Fig. 11, to prestress the rovings 46. When therovings have been prestressed, a molding compound consisting of amixture of resin and short stable glass fibres is introduced into themold cavity through a gate 53.

The short staple glass fibres may be of relatively short length, sayabout one-half A2) inch, for example, whereas, the length of theelongated prestressed rovings is greater than the overall length of thefinished blade. Preferably, both the elongated rovings and the shortstaple fibres are resin-coated or impregnated. The resin-impregnatedshort staple fibres are forced into mold cavity 49 under a very highpressure of the order of magnitude of two and r one-half (2 /2) tons persquare inch so that the short staple fibres and resin are forced aroundand through spaces between the fibres of the prestressed rovings to forma body and outer skin or blade surface and filling a root end cavity 54and encasing the pin 39. The mold pressure is sufiicient to compact theresin and short staple fibres around the rovings to form a solid blademass. While under pressure, the blade is heated to a sufficienttemperature to set the resin and form a hard infusible blade mass. Themolding compound preferably contains short staple glass fibres but maycontain a resin and other suitable short fibres.

In the finished blade 38, the short staple fibres form a section 54overlying and surrounding the prestressed rovings 46, as shown in Fig.12. The prestressed rovings are thus stressed in tension in the finishedcured blade, while the resin and short staple fibres in the vane portion56 of the blade (see Fig. 8) are stressed in compression.

In Fig. 13 is shown a blade 61 having a rigid metal key and pin member62 having an exposed metal key portion 63 which may be inserted in anappropriate key-shaped slot of a rotor. As shown in Fig. 14, the member62 is provided with a slot 64. The slot 64 divides the member 62 intothe key portion 63 and a pin portion 66 with the slot 64 therebetween.The portions 63 and 66 are connectcd together by end plate members 67and by a sufficient number of bridging members 68 to maintain themembers 63 and 66 in rigidly spaced relation. As shown, a portion of themember 63 is cut away, as indicated at 69, to form a gate through whichresin-impregnated short staple fibres are injected during molding of theblade 61.

The key and pin member is preferably formed of rigid forged metal or thelike.

As shown in Fig. 15, resin-impregnated doublets 71 are formed upon thepin 66 with the folds of the doublets extending through the slot 64. Thedoublets may be of fabric but preferably are rovings of glass fibers.The key and pin member 62 and the doublets of rovings 71 are disposed ina mold 72, as indicated in Fig. 16. As shown in Fig. 16, the mold 72includes a lower portion 73 and an upper portion 74 between which areformed two mold cavities 76 and 77. Free ends of the rovings 71 areclamped by means of clamps 78, and the clamps are urged away from thecenter of the mold to prestress the elongated rovings. Then,resin-impregnated short staple rovings are injected into the moldcavities through gate 79 to fill the mold cavities around the elongatedrovings. As shown in Fig. 18, in the finished blade, the elongatedrovings 71 are-surrounded by a mass or skin of resinimpregnated shortstaple rovings 81. In Fig. 18,'the mass 81 is exaggerated in size'forclarity of showing.

The blade 61 includes an exposed metal member 63 of key shape whichtakes the stress on the key portion of the blade when the blade is inuse.

The prestress load of each of the blades is preferably calculated to besufiicient so that the internal centrifugal force load of the bladeduring use is all taken by the prestressed elongated rovings, and theresin and short staple fibres remain under compression even when theblade is in rapid rotation during use. For a blade four (4) inches longand having a cross section area of one-quarter (l4) of a sc'iuar inchfor use in a rotor having a tip diameter of thifty-fiv (35) inchesandrotatioiial rate of eight thousand (8,000) R,, P. M.,, the p r estress load on the elongated rovings may be ap ma one thousand fifty (11050) pounds. The pfestressing; is suflicient to maintain centrifugalload off the resin of the blade within safe working limits. In otherwords, the prestress compression of the body of the blade will not besufiiciently dissipated when rotating within intended maximum speeds, tocause failure of the blade.

The compressor blades described above and illustrated in the drawingsare subject to structural modification without departing from the spiritand scope of the appended claims.

Having described my invention, what I claim as new, and desire to secureby Letters Patent is:

1. A prestressed airfoil rotor blade which comprises a rigid key and pinmember comprising an outer portion of key shape, a pin spaced from andsubstantially parallel to the outer portion, and bridging membersholding the key-shaped portion and the pin in spaced relation, aplurality of prestressed elongated rovings of doublet form, each doublethaving a loop at one end thereof mounted on said pin, and a cured resinimpregnating the rovings to hold the rovings in tension, the blade atthe doublet loops of the rovings being of key shape, the portion of therovings remote from the pin being of airfoil configuration.

2. The method of forming a blade having airfoil surfaces, the bladehaving a calculated centrifugal load capacity and being composed ofresin-impregnated fibres, that consists in laying resin-impregnatedfibres in a mold having a cavity shaped to the configuration of theblade, stressing the fibres in tension in a direction lengthwise of themold cavity to a load at least-equal to the calculated load capacity,closing the mold on the stressed fibres, and, While maintaining saidtensile load, heating the fibres to a temperature at which the resinsets.

3. The method of forming a cured resin airfoil rotor blade havingprestressed fibre glass reinforcement and a rigid metal root key and pinmember which comprises impregnating glass fibres with a resin, forming adoublet of said glass fibres about the root key and pin member, placingsaid glass fibres and root key and pin member in a die cavity, stressingthe fibres in tension substantially normally to the axis of the key andpin member and setting the resin while the glass fibres are stressed andmolding the resin between dies to mold the resin and glass fibres to anairfold blade shape.

4. A prestressed airfoil rotor blade which comprises a rigid key and pinmember comprising an outer portion of key shape, a pin spaced from andsubstantially parallel to the outer portion, and bridging membersholding the key-shaped portion and the pin in spaced relation, aplurality of prestressed, elongated rovings of doublet form, eachdoublet having a loop at one end thereof mounted on said pin, a curedresin impregnating the rovings to hold the rovings in tension, the bladeat the doublet loop of the rovings being of key-shape, and a mass ofresinimpregnated short staple fibre glass forming a skin surrounding theprestressed rovings, the portion of the blade remote from the pin beingof airfoil configuration.

5. The method of forming a cured resin airfoil rotor blade havingprestressed fibre glass reinforcement and a rigid metal root key thatcomprises impregnating rovings of glass fibres with aphenol-formaldehyde resin, forming a doublet of said impregnated rovingsto provide a loop at one end thereof, inserting a root pin through theloop, stressing the rovings in tension in a direction normal to the axisof the pin, covering said rovings and pin with a phenol-formaldehyderesin, applying heat and pressure to the same to impregnate the rovingsand form a hard, smooth surface on the blade while the rovings arestressed in tension, and setting the resin coating on the fibres in therovings to a hard and infusiblemass while the fibres of the rovings arein tension. x 6 The method of forming a cured resin airfoil rotorblade'h'aving prestressed fibre glass reinforcement and a rigid metalroot key that comprises impregnating" rovings of glass fibr es" with aphenol-formaldehyde resin, forming a'doublet of said impregnatedrovings; to provide a loop at one end thereof, inserting a root pinthrough the loop, stressing the rovings in tension in a direction normalto the axis of the pin, and covering said rovings with a mix ture ofphenol-formaldehyde resin and short staple glass fibres, and, while therovings are in tension, applying heat and pressure to the same toimpregnate the rovings and form a hard, infusible resin blade and rootsurface.

7. The method of forming a cured resin airfoil rotor blade havingprestressed fibre glass reinforcement and a rigid metal key and pinmember, that comprises impregnating rovings of glass fibres with aphenol-formaldehyde resin, forming a doublet of said impregnated rovingsto provide a loop atone end thereof, inserting a root key and pin memberthrough the loop, placing said rovings and member in a die cavity,stressing the rovings in tension in a direction normal to the axis ofthe root key and pin member, injecting an injectable phenol-formaldehyderesin molding compound into the die cavity through a gate underpressure, and applying heat to the mold to set and cure the resin whilethe rovings are stressed in tension to a hard, infusible mass throughoutthe blade and the rovings, and form a hard, smooth surface on the blade.

8. A method of forming an airfoil rotor blade which comprises forming acore of elongated, substantially parallel resin-impregnated rovings in amold cavity having a root end and a blade portion, the rovings extendinglengthwise of the blade portion, stressing said rovings in tension in adirection normal to the axis of the root end and lengthwise of the bladeportion of the mold cavity, injecting short fibre resin-impregnatedinjectable rovings through a gate into said mold cavity around saidelongated rovings to fill the root end of the cavity while the rovingsare stressed, and curing the resin to form a hard, smooth blade surface,whereby the resin holds the rovings in tension. j

9. A method of forming an airfoil rotor blade which comprises forming acore of elongated substantially parallel resin-impregnated rovings in amold cavity having a root end and a blade portion, the rovings extendinglengthwise of the blade portion and into the root end, the elongatedrovings partially filling the mold cavity, stressing the rovings intension in a direction normal to the axis of the root end and lengthwiseof the blade portion of the mold cavity, injecting short fibreresin-impregnated injectable rovings through a gate into said moldcavity around the elongated rovings to fill the mold cavity around theelongated rovings while the rovings are stressed in tension, and curingthe resin to form a hard smooth blade surface, whereby the resin holdsthe rovings in tension.

10. A method of forming an airfoil rotor blade which comprises forming acore of elongated resin-impregnated rovings with a return bend at oneend of the core about a transverse pin, the rovings extending from thepin into substantially parallel parts, the rovings being disposed in amold cavity having a root end portion and an elongated vane-formingportion with the return bend in the root end portion of the cavity andthe parallel parts extending lengthwise of the vane-forming portion,stressing the elongated rovings in tension in a direction normal to theaxis of the transverse pin, injecting short staple resinimpregnatedinjectable rovings through a gate into said mold cavity and around theelongated rovings while the rovings are stressed, and curing the resinto form a hard, smooth blade surface, whereby the resin holds theelongated rovings in tension.

(References on following page) References Cited in the file of thispatent 2,621,140

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